633
FXUS10 KWNH 010439
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1238 AM EDT MON JUN 01 2020
VALID JUN 01/0000 UTC THRU JUN 04/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
UPPER LEVEL TROUGH AND COLD FRONT ACROSS THE EASTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: MODERATE-HIGH
A PRONOUNCED UPPER LEVEL TROUGH BY EARLY JUNE STANDARDS WILL BE IN
PLACE ACROSS THE EASTERN U.S. TO BEGIN THE WEEK WITH A PRISTINE
AIRMASS IN PLACE, COURTESY OF A CANADIAN SURFACE HIGH. BY
TUESDAY, WARM AIR ADVECTION BEGINS IN EARNEST AS A WARM FRONT
SURGES EASTWARD WITH THE UPPER TROUGH DEPARTING. ALTHOUGH THERE
ARE SOME MINOR DIFFERENCES ONCE THE TROUGH REACHES EASTERN CANADA,
THERE IS EXCELLENT AGREEMENT FOR THE NORTHEAST U.S. THROUGH
TUESDAY BEFORE THE TROUGH LIFTS OUT, SO A GENERAL MODEL BLEND CAN
BE RECOMMENDED.
UPPER LEVEL LOW SLOWLY LIFTING FROM NORTHERN MEXICO INTO THE
SOUTHERN PLAINS EARLY THIS WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: MODERATE-HIGH
A BROAD UPPER LOW CURRENTLY SITUATED OVER NORTH-CENTRAL MEXICO
WILL SLOWLY LIFT NORTHWARD ACROSS TEXAS THROUGH TUESDAY EVENING,
AND THEN WEAKENS AS IT ENTERS THE BROAD UPPER RIDGE AXIS ACROSS
THE MID-SOUTH BY WEDNESDAY. THE MODELS ARE IN CLOSE ENOUGH
AGREEMENT ON THE MAIN FEATURES TO MERIT THE USE OF A
MULTI-DETERMINISTIC MODEL BLEND.
SLOW CUT-OFF LOW DEVELOPING WEST OF SOUTHERN CALIFORNIA THROUGH
MIDWEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z UKMET/ECENS MEAN
CONFIDENCE: MODERATE-HIGH
WITH THE FLOW PATTERN AMPLIFYING OFF THE WEST COAST OVER THE NEXT
FEW DAYS, AN UPPER LEVEL LOW IS FORECAST TO BECOME PINCHED OFF
FROM THE WESTERLIES FARTHER NORTH, AND THEN REMAIN NEARLY
STATIONARY THROUGH THE END OF THE WEEK, TRAPPED BY AN UPPER RIDGE
TO ITS EAST. THE MODELS OVERALL ARE IMPROVING WITH THE EVOLUTION
OF THIS LOW, WITH THE ECMWF/ECENS ONLY SLIGHTLY DISPLACED TO THE
WEST OF THE OTHER GUIDANCE. MOST OF THE ENSEMBLE SPREAD IS
CURRENTLY AMONG THE GEFS MEMBERS, AND OVERALL THE ENSEMBLE PLOTS
INDICATE THE BEST SUPPORT FOR THE 12Z UKMET SOLUTION, AND SOME OF
THE ECENS CAN ALSO BE INCORPORATED.
ACTIVE FLOW PATTERN NEAR THE U.S./CANADA BORDER
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/ECENS MEAN/00Z NAM
CONFIDENCE: MODERATE
THE WESTERLIES ON THE NORTHERN PERIPHERY OF THE CENTRAL U.S. RIDGE
ARE EXPECTED TO BE RATHER ACTIVE WITH THREE WELL DEFINED SHORTWAVE
DISTURBANCES TRACKING EASTWARD NEAR THE U.S./CANADA BORDER THROUGH
WEDNESDAY. THE FIRST SHORTWAVE, CURRENTLY NEAR ALBERTA, WILL
TRACK EASTWARD TO WESTERN ONTARIO BY TUESDAY MORNING AND WEAKEN.
THIS WILL BE QUICKLY FOLLOWED BY ANOTHER DISTURBANCE THAT IS
CURRENTLY NEAR THE PACIFIC NORTHWEST COAST AND FOLLOW A SIMILAR
PATH ACROSS SOUTH-CENTRAL CANADA. A THIRD SYSTEM WILL LIKELY
IMPINGE UPON THE PACIFIC NORTHWEST BY TUESDAY NIGHT AND THEN
RAPIDLY TRACK EASTWARD ALONG THE INTERNATIONAL BORDER.
GIVEN THE QUASI-ZONAL AND PROGRESSIVE FLOW PATTERN IN PLACE ACROSS
THE REGION, THIS IS WHERE THE GREATEST MODEL DIFFERENCES CURRENTLY
EXIST. THE 12Z CMC BECOMES SLOWER WITH THE FIRST SYSTEM BY AS
EARLY AS 18Z MONDAY AND THEN QUICKENS DAMPENS THE TROUGH. THE 00Z
GFS IS NOTED AS A STRONGER SOLUTION FOR THE SECOND AND THIRD
SHORTWAVES MOVING THROUGH, AND ALSO SUPPRESSES THE CENTRAL U.S.
RIDGE MORE COMPARED TO THE OTHER GUIDANCE. THE UKMET ALSO BECOMES
MORE AMPLIFIED WITH THE SECOND SYSTEM CROSSING THE NORTHERN GREAT
LAKES ON WEDNESDAY, AND FARTHER NORTH WITH THE SURFACE LOW
ASSOCIATED WITH THE THIRD SYSTEM. TAKING ALL OF THESE FACTORS
INTO ACCOUNT, BLENDING THE 12Z ECMWF/12Z ECENS/00Z NAM WOULD WORK
WELL AS A STARTING POINT IN THE FORECAST PROCESS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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